CBSE · Class 8 · Mathematics · Chapter 4

Quadrilaterals

Explore the properties, angle relationships and classifications of quadrilaterals through reasoning and construction.

13 lessons 55 min
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Lessons in this chapter

  1. 1Quadrilaterals and RectanglesRecognise quadrilaterals and build the rectangle definition from right angles and side relationships.
  2. 2The Diagonals of a RectangleUse congruence and angle reasoning to understand the diagonal properties of rectangles.
  3. 3Squares: Special RectanglesSee how a square extends rectangle properties with equal sides, perpendicular diagonals and angle bisection.
  4. 4Angles in a QuadrilateralDerive and apply the 360° interior-angle sum of quadrilaterals.
  5. 5Understanding ParallelogramsBuild the defining side and angle properties of parallelograms using parallel lines and congruence.
  6. 6Parallelogram DiagonalsExplore the central bisection property of parallelogram diagonals and use it in construction and reasoning.
  7. 7Rhombuses and Their AnglesUnderstand rhombuses through equal sides, parallelogram structure and angle relationships.
  8. 8The Diagonals of a RhombusUse perpendicular bisection and angle bisection to reason about and construct rhombuses.
  9. 9Building QuadrilateralsUse geoboards and joined triangles to build, predict and justify different quadrilateral types.
  10. 10KitesDefine kites and use their perpendicular-bisector and angle-bisector properties.
  11. 11TrapeziumsUse parallel-side relationships to understand trapeziums and the special isosceles trapezium.
  12. 12Which Quadrilateral Is It?Classify quadrilaterals using overlapping properties, set relationships and counterexamples.
  13. 13Chapter Summary and PracticeA complete revision of quadrilateral definitions, angle rules, diagonal properties, classifications and mixed problem solving.
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